Thanks a ton, Rob. The newsprint effect is still a little too regular for my tastes, but after fiddling with the displace filter a bit and a few other options, it's definitely a step in the right direction.

Something I discovered: if you're really concerned about the outlines of your shorelines, mask them off before doing the displace. The Y distort will still affect your east-west borders.

I'm experimenting now with using Tools|Color Tools|Threshold.. to add a little more blending between the woodcut lines where they meet the landmass, but that of course drops everything to black & white, which takes a bit of correction. Still, getting there!